/* See COPYRIGHT for copyright information. */

#include <inc/x86.h>
#include <inc/error.h>
#include <inc/string.h>
#include <inc/assert.h>

#include <kern/env.h>
#include <kern/pmap.h>
#include <kern/trap.h>
#include <kern/syscall.h>
#include <kern/console.h>
#include <kern/sched.h>

// Print a string to the system console.
// The string is exactly 'len' characters long.
// Destroys the environment on memory errors.
static void
sys_cputs(const char *s, size_t len)
{
	// Check that the user has permission to read memory [s, s+len).
	// Destroy the environment if not.

	// LAB 3: Your code here.
    user_mem_assert(curenv, s, len, PTE_P);

	// Print the string supplied by the user.
	cprintf("%.*s", len, s);
}

// Read a character from the system console without blocking.
// Returns the character, or 0 if there is no input waiting.
static int
sys_cgetc(void)
{
	return cons_getc();
}

// Returns the current environment's envid.
static envid_t
sys_getenvid(void)
{
	return curenv->env_id;
}

// Destroy a given environment (possibly the currently running environment).
//
// Returns 0 on success, < 0 on error.  Errors are:
//	-E_BAD_ENV if environment envid doesn't currently exist,
//		or the caller doesn't have permission to change envid.
static int
sys_env_destroy(envid_t envid)
{
	int r;
	struct Env *e;

	if ((r = envid2env(envid, &e, 1)) < 0)
		return r;
	env_destroy(e);
	return 0;
}

// Deschedule current environment and pick a different one to run.
static void
sys_yield(void)
{
	sched_yield();
}

// Allocate a new environment.
// Returns envid of new environment, or < 0 on error.  Errors are:
//	-E_NO_FREE_ENV if no free environment is available.
//	-E_NO_MEM on memory exhaustion.
static envid_t
sys_exofork(void)
{
	// Create the new environment with env_alloc(), from kern/env.c.
	// It should be left as env_alloc created it, except that
	// status is set to ENV_NOT_RUNNABLE, and the register set is copied
	// from the current environment -- but tweaked so sys_exofork
	// will appear to return 0.

	// LAB 4: Your code here.
    if (!curenv) {
        panic("called fork without curenv");
    }

    struct Env* newenv = 0;
    int r = env_alloc(&newenv, curenv->env_id);
    if (r)
        return r;
    if (r == -E_NO_FREE_ENV)
        panic("no free env to alloc");

    if (r == -E_NO_MEM)
        panic("no memory to alloc env");

    // set env status
    newenv->env_status = ENV_NOT_RUNNABLE;

    // copy registers from parent
    newenv->env_tf = curenv->env_tf;
    newenv->env_tf.tf_regs.reg_eax = 0;
    return newenv->env_id;
}

// Set envid's env_status to status, which must be ENV_RUNNABLE
// or ENV_NOT_RUNNABLE.
//
// Returns 0 on success, < 0 on error.  Errors are:
//	-E_BAD_ENV if environment envid doesn't currently exist,
//		or the caller doesn't have permission to change envid.
//	-E_INVAL if status is not a valid status for an environment.
static int
sys_env_set_status(envid_t envid, int status)
{
	// Hint: Use the 'envid2env' function from kern/env.c to translate an
	// envid to a struct Env.
	// You should set envid2env's third argument to 1, which will
	// check whether the current environment has permission to set
	// envid's status.

	// LAB 4: Your code here.
    struct Env* theEnv = 0;
    if (envid2env(envid, &theEnv, 1) < 0)
        return -E_BAD_ENV;

    if (status < ENV_FREE || status > ENV_NOT_RUNNABLE)
        return -E_INVAL;

    theEnv->env_status = status;
    return 0;
}

// Set envid's trap frame to 'tf'.
// tf is modified to make sure that user environments always run at code
// protection level 3 (CPL 3), interrupts enabled, and IOPL of 0.
//
// Returns 0 on success, < 0 on error.  Errors are:
//	-E_BAD_ENV if environment envid doesn't currently exist,
//		or the caller doesn't have permission to change envid.
static int
sys_env_set_trapframe(envid_t envid, struct Trapframe *tf)
{
	// LAB 5: Your code here.
	// Remember to check whether the user has supplied us with a good
	// address!
    
    struct Env* env = &envs[ENVX(envid)];
    if (env->env_status == ENV_FREE)
        return -E_BAD_ENV;

    // 检查envid是否可以访问tf
    struct PageInfo* info = page_lookup(env->env_pgdir, (void*)tf, NULL);
    if (info == NULL)
        return -E_BAD_ENV;
    
    // 检查传入的envid是否是
    memmove(&env->env_tf, tf, sizeof(*tf));
    return 0;
	//panic("sys_env_set_trapframe not implemented");
}

// Set the page fault upcall for 'envid' by modifying the corresponding struct
// Env's 'env_pgfault_upcall' field.  When 'envid' causes a page fault, the
// kernel will push a fault record onto the exception stack, then branch to
// 'func'.
//
// Returns 0 on success, < 0 on error.  Errors are:
//	-E_BAD_ENV if environment envid doesn't currently exist,
//		or the caller doesn't have permission to change envid.
static int
sys_env_set_pgfault_upcall(envid_t envid, void *func)
{
	// LAB 4: Your code here.
    struct Env* theEnv = 0;
    if (envid2env(envid, &theEnv, 1) < 0)
        return -E_BAD_ENV;

    // check permission
    if (curenv) {
        if ((curenv->env_tf.tf_cs & 0x3) > (theEnv->env_tf.tf_cs & 0x3))
            return -E_BAD_ENV;
    }

    theEnv->env_pgfault_upcall = func;
    
    return 0;
}

static int
has_perm(int tocheck, int perm){
    return (tocheck & perm) == perm;
}

static int
has_perm_other_than(int tocheck, int perm) {
    return (tocheck & ~(perm)) != 0;
}

// Allocate a page of memory and map it at 'va' with permission
// 'perm' in the address space of 'envid'.
// The page's contents are set to 0.
// If a page is already mapped at 'va', that page is unmapped as a
// side effect.
//
// perm -- PTE_U | PTE_P must be set, PTE_AVAIL | PTE_W may or may not be set,
//         but no other bits may be set.  See PTE_SYSCALL in inc/mmu.h.
//
// Return 0 on success, < 0 on error.  Errors are:
//	-E_BAD_ENV if environment envid doesn't currently exist,
//		or the caller doesn't have permission to change envid.
//	-E_INVAL if va >= UTOP, or va is not page-aligned.
//	-E_INVAL if perm is inappropriate (see above).
//	-E_NO_MEM if there's no memory to allocate the new page,
//		or to allocate any necessary page tables.
static int
sys_page_alloc(envid_t envid, void *va, int perm)
{
	// Hint: This function is a wrapper around page_alloc() and
	//   page_insert() from kern/pmap.c.
	//   Most of the new code you write should be to check the
	//   parameters for correctness.
	//   If page_insert() fails, remember to free the page you
	//   allocated!

    Debug("env[0x%x] at sys_page_alloc(0x%x, 0x%x, 0x%x)\n",
            curenv->env_id, envid,
            (uintptr_t)va, perm);
	// LAB 4: Your code here.
    struct Env* theEnv = 0;
    if (envid2env(envid, &theEnv, 1) < 0)
        return -E_BAD_ENV;

    // check va
    if (((uintptr_t)va & (PGSIZE-1)) != 0)
        return -E_INVAL;

    if (!has_perm(perm, PTE_P|PTE_U))
        return -E_INVAL;

    if (has_perm_other_than(perm, PTE_P|PTE_U|PTE_W|PTE_AVAIL))
        return -E_INVAL;

    struct PageInfo* page = page_alloc(ALLOC_ZERO);

    int r = page_insert(theEnv->env_pgdir, page, va, perm);

    if (r < 0)
        return -E_NO_MEM;
    return 0;
}

// Map the page of memory at 'srcva' in srcenvid's address space
// at 'dstva' in dstenvid's address space with permission 'perm'.
// Perm has the same restrictions as in sys_page_alloc, except
// that it also must not grant write access to a read-only
// page.
//
// Return 0 on success, < 0 on error.  Errors are:
//	-E_BAD_ENV if srcenvid and/or dstenvid doesn't currently exist,
//		or the caller doesn't have permission to change one of them.
//	-E_INVAL if srcva >= UTOP or srcva is not page-aligned,
//		or dstva >= UTOP or dstva is not page-aligned.
//	-E_INVAL is srcva is not mapped in srcenvid's address space.
//	-E_INVAL if perm is inappropriate (see sys_page_alloc).
//	-E_INVAL if (perm & PTE_W), but srcva is read-only in srcenvid's
//		address space.
//	-E_NO_MEM if there's no memory to allocate any necessary page tables.
static int
sys_page_map(envid_t srcenvid, void *srcva,
	     envid_t dstenvid, void *dstva, int perm)
{
	// Hint: This function is a wrapper around page_lookup() and
	//   page_insert() from kern/pmap.c.
	//   Again, most of the new code you write should be to check the
	//   parameters for correctness.
	//   Use the third argument to page_lookup() to
	//   check the current permissions on the page.

    Debug("env[0x%x]@sys_page_map(0x%x, 0x%x, 0x%x, 0x%x, 0x%x)\n",
            curenv->env_id,
            srcenvid, (uintptr_t)srcva, dstenvid, (uintptr_t)dstva, perm);
	// LAB 4: Your code here.
    struct Env* srcenv = 0;
    struct Env* dstenv = 0;
    if (envid2env(srcenvid, &srcenv, 0) < 0)
        return -E_BAD_ENV;

    if (envid2env(dstenvid, &dstenv, 0) < 0)
        return -E_BAD_ENV;

    if ((uintptr_t)srcva >= UTOP || ((uintptr_t)srcva & (PGSIZE-1)) != 0)
        return -E_INVAL;

    if ((uintptr_t)dstva >= UTOP || ((uintptr_t)dstva & (PGSIZE-1)) != 0)
        return -E_INVAL;

    pte_t* a_pte = 0;
    struct PageInfo* srcpage = page_lookup(srcenv->env_pgdir, srcva, &a_pte);
    if (!srcpage)
        return -E_INVAL;
    if ((perm & PTE_W) && !((*a_pte) & PTE_W))
        return -E_INVAL;

    if (!has_perm(perm, PTE_U|PTE_P))
        return -E_INVAL;

    if (has_perm_other_than(perm, PTE_P|PTE_U|PTE_W|PTE_AVAIL))
        return -E_INVAL;

    if (page_insert(dstenv->env_pgdir, srcpage, dstva, perm) < 0)
        return -E_NO_MEM;

    return 0;
}

// Unmap the page of memory at 'va' in the address space of 'envid'.
// If no page is mapped, the function silently succeeds.
//
// Return 0 on success, < 0 on error.  Errors are:
//	-E_BAD_ENV if environment envid doesn't currently exist,
//		or the caller doesn't have permission to change envid.
//	-E_INVAL if va >= UTOP, or va is not page-aligned.
static int
sys_page_unmap(envid_t envid, void *va)
{
	// Hint: This function is a wrapper around page_remove().

	// LAB 4: Your code here.
    struct Env* theEnv = 0;
    if (envid2env(envid, &theEnv, 1) < 0)
        return -E_BAD_ENV;

    if ((uintptr_t)va >= UTOP || (uintptr_t)va & (PGSIZE-1))
        return -E_INVAL;

    // check permission by comparing curenv's cs and envid's cs
    if (curenv) {
        if ((curenv->env_tf.tf_cs & 0x3) > (theEnv->env_tf.tf_cs & 0x3))
            return -E_BAD_ENV;
    }

    page_remove(theEnv->env_pgdir, va);
    return 0;
}

/**
 * 用于确定是否需要传输数据页
 */
static int
require_ipc_page(struct Env* env) {
    if ((uintptr_t)env->env_ipc_dstva >= UTOP)
        return 0;
    return 0;
}

// Try to send 'value' to the target env 'envid'.
// If srcva < UTOP, then also send page currently mapped at 'srcva',
// so that receiver gets a duplicate mapping of the same page.
//
// The send fails with a return value of -E_IPC_NOT_RECV if the
// target is not blocked, waiting for an IPC.
//
// The send also can fail for the other reasons listed below.
//
// Otherwise, the send succeeds, and the target's ipc fields are
// updated as follows:
//    env_ipc_recving is set to 0 to block future sends;
//    env_ipc_from is set to the sending envid;
//    env_ipc_value is set to the 'value' parameter;
//    env_ipc_perm is set to 'perm' if a page was transferred, 0 otherwise.
// The target environment is marked runnable again, returning 0
// from the paused sys_ipc_recv system call.  (Hint: does the
// sys_ipc_recv function ever actually return?)
//
// If the sender wants to send a page but the receiver isn't asking for one,
// then no page mapping is transferred, but no error occurs.
// The ipc only happens when no errors occur.
//
// Returns 0 on success, < 0 on error.
// Errors are:
//	-E_BAD_ENV if environment envid doesn't currently exist.
//		(No need to check permissions.)
//	-E_IPC_NOT_RECV if envid is not currently blocked in sys_ipc_recv,
//		or another environment managed to send first.
//	-E_INVAL if srcva < UTOP but srcva is not page-aligned.
//	-E_INVAL if srcva < UTOP and perm is inappropriate
//		(see sys_page_alloc).
//	-E_INVAL if srcva < UTOP but srcva is not mapped in the caller's
//		address space.
//	-E_INVAL if (perm & PTE_W), but srcva is read-only in the
//		current environment's address space.
//	-E_NO_MEM if there's not enough memory to map srcva in envid's
//		address space.
static int
sys_ipc_try_send(envid_t envid, uint32_t value, void *srcva, unsigned perm)
{
	// LAB 4: Your code here.
    Debug("[%x] send to [%x]\n", curenv->env_id, envid);
    int r;
    struct Env* recv_env = 0;
    if ((r = envid2env(envid, &recv_env, 0)) < 0) {
        return -E_BAD_ENV;
    }

    if (!recv_env->env_ipc_recving)
        return -E_IPC_NOT_RECV;

    uintptr_t src_va = (uintptr_t)srcva;
    if (src_va < UTOP && (src_va & (PGSIZE-1))){
        return -E_INVAL;
    }

    /*
    if (user_mem_check(curenv, srcva, 1, perm)) {
        cprintf("user_mem_check error with srcva: %x\n", srcva);
        return -E_INVAL;
    }
    */

    // the page must exists because we checked
    pte_t* a_pte = pgdir_walk(curenv->env_pgdir, srcva, 0);
    if (require_ipc_page(recv_env) && (perm & PTE_W) &&
            *a_pte != (PTE_W | *a_pte)) {
        return -E_INVAL;
    }

    // check done, start process
    recv_env->env_ipc_value = value;
    recv_env->env_ipc_perm = perm;
    if ((uintptr_t)(recv_env->env_ipc_dstva) < UTOP) {
        // map physical page of srcva to dstva in the receiving env
        r = sys_page_map(curenv->env_id, srcva,
                recv_env->env_id, recv_env->env_ipc_dstva, perm);
        if (r == -E_NO_MEM)
            return r;
    }

    recv_env->env_ipc_from = curenv->env_id;

    // wake up the receiving env
    // tweak the receiving to return 0
    recv_env->env_tf.tf_regs.reg_eax = 0;
    recv_env->env_status = ENV_RUNNABLE;
    recv_env->env_ipc_recving = 0;

    return 0;
}

// Block until a value is ready.  Record that you want to receive
// using the env_ipc_recving and env_ipc_dstva fields of struct Env,
// mark yourself not runnable, and then give up the CPU.
//
// If 'dstva' is < UTOP, then you are willing to receive a page of data.
// 'dstva' is the virtual address at which the sent page should be mapped.
//
// This function only returns on error, but the system call will eventually
// return 0 on success.
// Return < 0 on error.  Errors are:
//	-E_INVAL if dstva < UTOP but dstva is not page-aligned.
static int
sys_ipc_recv(void *dstva)
{
	// LAB 4: Your code here.
    // mark as not runnable to block
    if ((uintptr_t)dstva < UTOP && ((uintptr_t)dstva & (PGSIZE-1))) 
        return -E_INVAL;

    curenv->env_status = ENV_NOT_RUNNABLE;
    curenv->env_ipc_recving = 1;
    curenv->env_ipc_dstva = (dstva == 0 ? (void*)-1 : dstva);
    /*
    cprintf("env[%x] is recving with dstva[%x]\n", curenv->env_id, 
            curenv->env_ipc_dstva);
    */

    sys_yield();
	return 0;
}

// Dispatches to the correct kernel function, passing the arguments.
int32_t
syscall(uint32_t syscallno, uint32_t a1, uint32_t a2, uint32_t a3, uint32_t a4, uint32_t a5)
{
	// Call the function corresponding to the 'syscallno' parameter.
	// Return any appropriate return value.
	// LAB 3: Your code here.

	//panic("syscall not implemented");

	switch (syscallno) {
        case SYS_cputs:
            sys_cputs((const char*)a1, (size_t)a2);
            break;
        case SYS_cgetc:
            return sys_cgetc();
        case SYS_getenvid:
            return sys_getenvid();
        case SYS_env_destroy:
            return sys_env_destroy((envid_t)a1);
        case SYS_yield:
            sys_yield();
            break;
        case SYS_exofork:
            return sys_exofork();
        case SYS_page_alloc:
            return sys_page_alloc((envid_t)a1, (void*)a2, (int)a3);
        case SYS_page_map:
            return sys_page_map((envid_t)a1, (void*)a2,
                    (envid_t)a3, (void*)a4, (int)a5);
        case SYS_page_unmap:
            return sys_page_unmap((envid_t)a1, (void*)a2);
        case SYS_env_set_status:
            return sys_env_set_status((envid_t)a1, (int)a2);
        case SYS_env_set_pgfault_upcall:
            return sys_env_set_pgfault_upcall((envid_t)a1, (void*)a2);

        case SYS_ipc_try_send:
            return sys_ipc_try_send((envid_t)a1, (uint32_t)a2,
                    (void*)a3, (unsigned)a4);
        case SYS_ipc_recv:
            return sys_ipc_recv((void*)a1);
        case SYS_env_set_trapframe:
            return sys_env_set_trapframe((envid_t)a1, (struct Trapframe*)a2);



        case NSYSCALLS:
            return -E_INVAL;
	default:
		return -E_INVAL;
	}

    return 0;
}

